A basic component within any communication receiver is the demodulator. For digital communications one of two prior art demodulator design concepts is typically employed. The first approach requires translating the received signal to baseband while the second approach operates on the signal at some selected intermediate frequency (IF). Complexities and limitations in both approaches are evidence of the need for improved demodulation techniques.
Recent advances in charge-coupled-device (CCD) technology have spawned new concepts in a variety of technical areas. Application of this technology to issues facing the communications industry has resulted in the discovery of new solutions to problems in digital communications. The objective of this invention is to provide a new demodulation method and apparatus which offers a number of enhancements. The invention correlates time ordered samples of a received signal with a preselected tap weight sequence to yield maximum correlation energy when desired alignment occurs to thereby mark phase and frequency agreement between local timing and the received signal. In a preferred embodiment, the invention employs charge-coupled-device technology for demodulation. Benefits over traditional approaches, including improved performance and reduced complexity, are realized by this invention. The benefits of a CCD based demodulation approach over traditional methods are presented in the following sections.
Several aspects of this invention provide enhancements over traditional methods. Some of these areas of enhancement include performance, implementation, reliability, cost, size and power consumption. The following is a summary of some of the more prominent features of this invention: